Amebiasis is a parasitism provoked by the protozoan Entamoeba histolytica. It affects mainly the inhabitants of developing countries. Under appropriate conditions which are not well known, trophozoites differentiate to an infective form or cyst which is excreted with excrements and this way can infect a new host by oral food, water or person to person transmission. Most of the people infected with Entamoeba histolytica are asymptomatic, but in 10% of the people with amebiasis, the parasite produces sickness when it invades the intestinal mucosity producing amoebic colitis or more dangerous damage when the amebiasis is extraintestinal and there is a dissemination of the protozoan to the liver, provoking an amoebic liver abscess. In the cases in which there is a perforation of the liver or the intestine, it can provoke pleural damage, pericarditis, peritonitis and even death. Amebiasis occupies the sixth place among the most frequent causes of death in Mexico. In Mexico as in Venezuela 2% to 15% of the cases of children with diarrhea which have been subjected to hospitalization, have been associated with an Entamoeba histolytica infection.
To effect correct epidemiological studies, it will require the development of diagnostic methods which are sensitive and specific. The coproparasitoscopic diagnosis of Entamoeba histolytica is especially difficult because it requires highly skilled workers to prevent false interpretations. The serologic diagnosis is not effective because the existing tests are not sensitive enough, especially when they are used in highly endemic zones. To obtain really useful diagnostic tests, it is necessary to know the amoebic molecules that are actively involved in the cases of invasive amebiasis and to generate with these molecules effective diagnostic tests. Knowing these molecules, studies can be made on their intervention in the immune protection mechanisms generated against amoebas and the possible implementation of vaccines. A major impediment to achieve this goal is represented by the highly elevated enzymatic activity of the proteases present in the amoebic extracts (McLaughlin & Faubert, G., 1977, "Partial purification and some properties of a neutral sulfhydril and an acid proteinase from Entamoeba histolytica" are disclosed in Canadian Journal of Microbiology, 23, 420-425, and Perez-Monfort, Ostoa-Saloma, P. Velazquez-Medina, L. Montort I & Becker, I., 1987, "Catalytic classes of proteinases of Entamoeba histolytica" Molecular and Biochemical Parasitology, 6, 87-97). The proteases degrade proteins in the amoebas giving random products of degradation and make, if not impossible at least very difficult, to standarize the methods of fine analysis of antigenicity. To avoid the enzyme activity, enzymatic inhibitors are used, but they have the inconvenience that they are not totally effective, that they permit working with extracts only for relatively short periods of time and they do not give the opportunity to store the same samples for later tests. The procedures that we wish to patent is based on the method to remove the lipids, described by Said-Fernandez, S. and Lopez-Revilla R. (Said-Fernandez, S and Lopez-Revilla R. (1979) "Characteristic protein electrophoretic patterns of four Entamoeba strains", (Zeitschrift fur Parasitenkunde, 56. 219-225). The method of the invention relates to the preservation of amoebic antigens, without using enzymatic inhibitors, which is the method presently used to preserve amebic antigens for further study.